DUI (driving under the influence), DWI (driving while intoxicated), and OWI (operating while intoxicated) are similar criminal offenses that involve the operation of a motor vehicle, electric vehicle, or sometimes an otherwise-powered vehicle—including boats, aircraft, and bicycles—by an operator who is under the influence of or intoxicated by alcohol or drugs. Per se (pronounced purr-say) intoxication is intoxication by definition—as defined in the state’s statutes by blood alcohol concentration (BAC) of .08 or more (.05 in Utah). And even if a person is not per se intoxicated, they may be intoxicated by not having the normal use of their mental or physical faculties (abilities), for example, and may be charged with a criminal offense.
In some contexts the terms DUI and DWI are used interchangeably, with some states using one term and other states using the other term to define what is essentially the same criminal offense. But in some states both criminal charges are available and there is a legal distinction between them.
For example, in some states with both criminal offenses, DUI is the criminal offense of operating a vehicle under the influence of prescription or recreational drugs, and DWI is the offense of operating a vehicle while intoxicated by alcohol. In some states DWI refers to per se intoxication when the driver’s BAC is above the threshold defined by statute—.08 (.05 in Utah)—and DUI is a criminal offense charged when the police officer believes the driver is under the influence of alcohol, despite the driver’s BAC being below the statutory threshold of .08. And in some states DUI is a separate offense for drivers under the legal age of drinking (21) who have some alcohol in their system, but less than a .08 BAC.
These and other similar alcohol-related operating offenses—including aggravated or enhanced forms of these offenses—vary from state to state in their definitions and potential punishments and are generally located in a state’s statutes—often in the penal code or criminal code.
In Massachusetts, the terms OUI (Operating Under the Influence), DUI (Driving Under the Influence), and DWI (Driving While Intoxicated) are used to describe the criminal offense of operating a motor vehicle while impaired by alcohol or drugs. Massachusetts law does not distinguish between DUI and DWI as separate offenses; instead, it uses the term OUI to encompass all forms of impaired driving. The legal limit for blood alcohol concentration (BAC) in Massachusetts is .08 for drivers 21 and over, and any BAC at or above this level is considered per se intoxication. For drivers under the age of 21, the state has a 'zero tolerance' law with a lower BAC limit of .02. Operating a vehicle with a BAC at or above the legal limit can result in criminal charges, and penalties can include fines, license suspension, and even imprisonment. Additionally, Massachusetts law allows for enhanced penalties for aggravated forms of OUI, such as operating with a BAC of .15 or higher, or causing serious injury or death while operating under the influence.